Axial quasinormal modes of neutron stars in R2 gravity

Abstract

The spectrum of frequencies and characteristic times that compose the ringdown phase of gravitational waves emitted by neutron stars carry information about the matter content (the equation of state) and the underlying theory of gravity. Typically, modified theories of gravity introduce additional degrees of freedom/fields, such as scalars, which result in new families of modes composing the ringdown spectrum. One simple but physically promising candidate is R 2 gravity, which effectively introduces an additional massive scalar field that couples non-minimally to gravity, resulting in scalarized neutron stars. Here we show that the ringdown spectrum of R 2 neutron stars is much richer and fundamentally different from the spectrum in GR, possessing for instance ultra long lived modes that can propagate away from the star in the form of scalar gravitational radiation.

New exact traversable wormhole solution to the Einstein-scalar-Gauss-Bonnet equations coupled to power-Maxwell electrodynamics

“…Alternatively, in [14], was shown that the Ellis wormhole also can be understood as an electrovacuum solution of EsGB gravity with a material source consisting of a source-free electric field and a real scalar field. The Ellis WH have been extensively studied, and its properties like gravitational lensing [15], quasi-normal modes [16], stability [17] and shadows [18], have been thoroughly investigated. In this case the metric (16) reduces to…”

Boson and Dirac stars in D ≥ 4 dimensions

“…Note that in the above equations (29)-(31) we have fixed the "spirality" to +1, the only case discussed in this work. Nonetheless, all the qualitative properties of the Dirac stars that we present in the next Section are not affected by this choice (for instance, other properties of the Dirac field on static and spherically symmetric configurations, such as the quasinormal modes, are not qualitatively affected by the change of spirality [15]).…”

“…These angular solutions are the spinor monopole harmonics for a (D − 2)-sphere[14]; also, they are related with the solutions of the angular part in[15].…”

“…The representation of the angular γ matrices is that employed in[15] 4. However, let us comment here that in the field equations, the phase ofφ plays no role, and thus one can choose without loss of generalityφ to be a real function).…”

Reconstruction of the neutron star equation of state from w -quasinormal modes spectra with a piecewise polytropic meshing and refinement method

“…In these papers, an efficient method to calculate the QNM spectra was presented. This method was also applied to study QNMs in alternative theories ( [16], [17], [18], [19], [20]). Here we will present an enhancement of the method that will allow us to calculate the w-QNM spectra of thousands of EOSs in a reasonable time.…”